Ch. 10 - Photosynthesis

Freeman - Biological Science 8th Edition

Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook

Freeman 8th Edition

Ch. 10 - Photosynthesis

Problem 7

Chapter 10, Problem 7

Apply what you know of the relationship between the light-capturing reactions and the Calvin cycle to calculate the number of photons used to produce a new G3P and regenerate RuBP. (Assume 1 ATP is produced for each pair of electrons used to form NADPH.)

Verified step by step guidance

Step 1: Understand the relationship between light-capturing reactions and the Calvin cycle. In the light-capturing reactions, light energy is used to produce ATP and NADPH. These are then used in the Calvin cycle to produce G3P and regenerate RuBP.

Step 2: Calculate the number of ATP and NADPH needed to produce a new G3P and regenerate RuBP. For each G3P molecule produced, 9 ATP and 6 NADPH are required. To regenerate RuBP, an additional 3 ATP are needed. So, a total of 12 ATP and 6 NADPH are needed.

Step 3: Calculate the number of photons needed to produce ATP and NADPH. Each ATP requires 2 photons, and each NADPH requires 2 photons (since 1 ATP is produced for each pair of electrons used to form NADPH). Therefore, 24 photons are needed for ATP and 12 photons for NADPH.

Step 4: Add the number of photons needed for ATP and NADPH to get the total number of photons used. So, 24 photons for ATP + 12 photons for NADPH = 36 photons.

Step 5: Therefore, 36 photons are used to produce a new G3P and regenerate RuBP.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

53s

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Light-Capturing Reactions

The light-capturing reactions, also known as the light-dependent reactions, occur in the thylakoid membranes of chloroplasts. These reactions convert light energy into chemical energy in the form of ATP and NADPH. Photons are absorbed by chlorophyll, exciting electrons that are transferred through a series of proteins, ultimately leading to the production of ATP and NADPH, which are essential for the subsequent Calvin cycle.

Calvin Cycle

The Calvin cycle, or light-independent reactions, takes place in the stroma of chloroplasts and utilizes ATP and NADPH produced in the light-capturing reactions to convert carbon dioxide into glucose. The cycle involves three main phases: carbon fixation, reduction, and regeneration of RuBP. For every three molecules of CO2 that enter the cycle, one molecule of G3P is produced, which can be used to form glucose and other carbohydrates.

Photon Requirement for G3P Production

To produce one molecule of G3P, the Calvin cycle requires a specific number of ATP and NADPH, which are generated from the light-capturing reactions. Each pair of electrons used to form NADPH corresponds to the absorption of two photons, while ATP production is also linked to photon absorption. Therefore, calculating the total number of photons involves understanding the stoichiometry of ATP and NADPH used in the cycle, as well as their relationship to the number of G3P molecules produced.

Recommended video:

Guided course

04:36

Primary Production in Aquatic Ecosystems

Related Practice

Textbook Question

Predict how the following conditions would affect the production of O₂, ATP, and NADPH and state whether noncyclic or cyclic electron flow would occur in each:

(2) blue and red photons hit a chloroplast, but no NADP⁺ is available

views

Textbook Question

At what point in photosynthesis is the electromagnetic energy of light first converted into chemical energy?

views

Textbook Question

Why is the chlorophyll in chloroplasts less likely to produce fluorescence compared to extracted chlorophyll molecules?

Textbook Question

Describe the three phases of the Calvin cycle and how the products of the light-capturing reactions participate in this process.

Textbook Question

Which of the following correctly identify a role of the ATP produced in the light-capturing reactions? Select True or False for each statement.

T/F It is used by rubisco to fix CO₂ to RuBP.

T/F It serves the same role as ATP produced by mitochondria.

T/F It is used to regenerate RuBP from G3P molecules.

T/F It is used to produce G3P molecules

views

Textbook Question

Predict how the following conditions would affect the production of O₂, ATP, and NADPH and state whether noncyclic or cyclic electron flow would occur in each:

(1) Only blue photons hit a chloroplast

views